Telephone transmission system.



A. B. SMITH.

TELEPHONE TRANSMISSION SYSTEM.

APPLICATION FILED JUNE 9. 1913.

1,178,472. Patented Apr. 4, 1916.

llllllllllll WITNESSES fivx/zA/To c- \HTTOIF/VEYSL UNITED STATES PATENT OFFICE.

ARTHUR BESSEY SMITH, or EVANSTON, ILLINOIS, ASSIGNOR T0 JOHN B. RUSSELL, or

. N'EW yonx, N. Y.

TELEPHONE TRANSMISSION SYSTEM.

Specification of Letters Patent.

Application filed June 9, 1913. Serial No. 772,474.

To all whom it may concern:

Be it known that I, ARTHUR Bnssnv SMITH, a citizen of the United States of America, and resident of Evanston, Cook 5 county, Illinois, have invented a certain new and useful Improvement in Telephone Transmission Systems, of which the following is a specification.

My invention relates to improvements in 10 telephone transmitting circuits, and more particularly to a system for use in loud speaking annunciator systems, or 1n systems in which music is to be transmitted over the wire. In such systems it is often desirable to transmit sounds simultaneously from a number of sepa'ratesources or places to a single receiving circuit. For instance, it might be desired to transmit a song produced by a quartette, in which case better results are obtained if a separate transmitter is employed for each person than if an attempt is made to have all four persons singinto one transmitter. Of course, the combination of these transmitters might be obtained by merely connecting them in multiple, but I have found by experiment that the best results are not obtained by this method. I have, however, devised a very efficient method in which a number of transmitters can be combined in such a mannor that their combined effect is impressed upon a receiving circuit. In this connection I employ the usual differential type of transmitter-that is, the type of transmitter provided with three electrodes, the middle electrode being movable with respect to the two outer electrodes. These transmittersare then arranged in the form of a well-known \Vheatstone bridge.

My invention will be more clearly understood by reference to the accompanying' drawings, in which I have shown in diagrammatic form two modifications of my invention employing, respectively, four and eight transmitters.

In Figure 1 there are shown four transmitters a, b, c and d of the differential multiple electrode t pe. These transmitters may be of any 0 the well-known types of construction and are represented herein diagrammatically by three electrodes. These electrodes may be controlled by the usual diaphragm in any of the well-known manners. For example, the middle electrode may be stationary and the two outer ones movable with the diaphragm, or vice versa. The four transmitters are connected in series in a closed circuit. The receiver 6 is connected between the middle electrodes 71 and (Z of the transmitters Z) and 11. .A condenser f is preferably included. in "this connection. Connected across the middle electrodes 0 and a of the transmitters c a d a there is a battery B. A regulating rsistance g is included in this latter connection. This reslstance may be an electric lamp or coil of wire, or any other suitable resistance, or, 1f the battery shown is of the proper potentlal, this resistance may be dispensed with. It will be seen that these connections form the well-known \Vheatstone bridge in which each arm comprises one resistance element or microphone cell of each of two transnitters. If, now, sound waves are directed mto any one of the transmitters, the consequent vibration of its diaphragm and electrodes alters the resistance in two arms of the bridge and thereby alters the potential at the terminals of the receiver 0', thus settmg up vibratory currents therein in accordance with the sounds impressed on the transmitter. The effect on the receiver will be practically the same, no matter into which transmitter the sound is directed. If different sounds are directed into each of the four transmitters, the receiver will respond to all four simultaneously, and the effect of all will be uniformly blended together.

The arrangement in Fig. 2 is the same as that in Fig. 1, except that there are eight transmitters arranged in pairs, the two transmitters of each pair being connected in multiple. By this arrangement the receiver may be made to respond to eight separate sources of sound, each of which may act upon a separate transmitter. For example, if. eight persons desire to talk or sing into the apparatus at one time, each may use an individual transmitter. If only four persons are to speak into the apparatus, each may use two transmitters, using, preferably, one out of each of the two pairs on opposite sides of the bridge. For example, if the transmitters are to be used in pairs, n or 3' should be used with either It or Z and m or c with is or o. By thus combinin two transmitters on the opposite sides 0 the bridge, the general balance of the bridge is maintained more closely than if the two transmitters on one side are used together.

It will, of course, be understood that instead of employing but a single receiver, if desired a plurality of receivers could be connected across the bridge, either in multiple or in series. Furthermore, it will be seen that the drawing is merely intended to represent the electrical connections of the transmitters and receivers and not their mechanical or physical relations or positions.

The recelvers and transmitters herein shown can be of any well-known form, and my invention is not limited to the type of receiver shown, and is only limited by the fact that the transmitters should be of the differential or multiple electrode type.

What I claim as my invention is:

1. In a telephone system, a plurality of transmitters each having three electrodes, a battery having its opposite poles connected to the middle electrode of two of said transmitters, and a receiver bridged between the central electrode of two more of said-transmitters.

2. In a telephone system, two pairs of differential transmitters, a battery bridged across the central electrodes of one pair, a receiver bridged across the central electrodes of the second pair, and connections between each transmitter of one pair and each of the transmitters of the second pair.

3. In a telephone system, four transarrears mitters connected in' series in a closed cir cuit, each of said transmitters having front and back electrodes and a central electrode, a battery bridged across the central electrodes of the two alternate transmitters, and a receiver bridged across the central electrodes of the other two transmitters.

4. In a telephone system, four transmitters connected in series in a closed circuit, a transmitter connected in multiple with each of said four transmitters, said transmitters each comprising front, back and central electrodes, a battery bridged across the central electrodes of two alternate pairs of transmitters, and a receiver bridged across the central electrodes of the remaining two pairs of transmitters.

5. In a telephone system, a plurality of difi'erential transmitters arranged in the form of a VVheatstone bridge, each of the four sides of which bridge includes a half of two of said transmitters in series, and a telephone receiver bridged across the middle point of two opposite transmitters.

Signed by me at Chicago, Cook county, Illinois, this 3rd day of June, 1913.

ARTHUR BESSEY SMITH.

Witnesses:

J. D. Fares, ALBERT ANDERSON. 

